1. Field of the Invention
The present invention relates to process cartridges and electrophotographic image forming apparatus.
2. Description of the Related Art
The electrophotographic image forming apparatus described herein is an apparatus for forming an image on a recording medium by the electrophotographic image forming method. Examples of the electrophotographic image forming apparatus include, for example, electrophotographic copiers, electrophotographic printers (e.g., laser beam printers, LED printers, etc.), facsimile machines, word processors, and so on.
The process cartridges are cartridges in which at least developing means and an electrophotographic photosensitive drum are integrally built and which can be mounted onto or dismounted from the main body of an imaging forming apparatus. Further, process cartridges are cartridges in which at least cleaning means, charging means, and developing means as process means and the electrophotographic photosensitive drum are integrally built and which can be mounted onto or dismounted from the main body of the apparatus.
In the electrophotographic image forming apparatus using the electrophotographic image forming method, the electrophotographic photosensitive body uniformly charged by the charging means is subjected to selective exposure according to image information to form a latent image thereon.
Then the latent image is developed with toner by the developing means to form a toner image. Thereafter, the toner image formed on the electrophotographic photosensitive body is transferred onto a recording medium by the transferring means to form an image thereon.
The conventional image forming apparatus using the electrophotographic image forming process was constructed in the process cartridge system wherein the electrophotographic photosensitive body of drum shape and the process means acting on the electrophotographic photosensitive body were integrally built in a cartridge and this cartridge was mountable onto or dismountable from the main body of the image forming apparatus. This process cartridge system has permitted the user to perform the maintenance of the apparatus by himself or herself without any help from a service technician. Therefore, the process cartridge system enhanced operability remarkably. This process cartridge system is thus commonly used in the image forming apparatus.
A typical configuration of such process cartridges is such that two frames are coupled to each other. For example, a cleaning frame (first frame), which supports the photosensitive drum, the charging device, and the cleaning device, and another frame (second frame), which is a joint unit consisting of a developing frame for supporting the developing means and a toner frame having a toner chamber, are coupled to each other so as to be rotatable about a fulcrum. Then the two frames are biased around the fulcrum by elastic members such as springs or the like to determine relative positions of the photosensitive drum and the developing means. The functional advantages of the above structure include the optimization of pressure of the developing roller against the photosensitive drum, the capability of maintaining a clearance between the surface of the photosensitive drum and the surface of the developing roller, etc. and, on the other hand, the two-piece structure provides many merits of facilitating forming of the frames, facilitating assembly, and so on.
The present invention is a further development of the related art as described above. In the case of the conventional two-frame structure with coupling holes (through holes), there were cases where shavings of resin made during a press fit work of coupling pins to couple the two frames dropped into the interior of the process cartridge. This increased inconvenience in manufacturing, e.g., a need for an additional cleaning step in assembly.
An object of the present invention is to provide a process cartridge that is comprised of a first frame and a second frame and that can prevent shavings, made during press fitting of a coupling pin to couple the first frame to the second frame, from dropping through a press fit hole into the interior of the process cartridge.
Another object of the present invention is to provide a process cartridge that is comprised of a first frame and a second frame and that is configured to let air flow out of a press fit hole during press fitting of a coupling pin to couple the first frame to the second frame, thereby making the fastening force firm and secure with the coupling pin.
Another object of the present invention is to provide a process cartridge that is comprised of a first frame and a second frame and that is configured to prevent shavings, made during a press fitting of a coupling pin to couple the first frame to the second frame, from dropping through a press fit hole into the interior of the process cartridge and simultaneously to let air flow out of the press fit hole during the press fitting of the coupling pin, thereby making the fastening force firm and secure with the coupling pin.
Another object of the present invention is to provide a process cartridge and electrophotographic image forming apparatus comprising:
an electrophotographic photosensitive drum;
a developing member for developing an electrostatic latent image formed on the electrophotographic photosensitive drum, with toner;
a first frame for supporting the electrophotographic photosensitive drum;
a second frame for supporting the developing member;
a coupling pin for coupling the first frame to the second frame to be rotatable relative to each other;
a first hole through which the coupling pin penetrates and which is provided in the first frame;
a second hole into which the coupling pin is press-fitted and which is provided in the first frame; and
a closed portion provided at a leading end of the coupling pin in a press fit direction in order to close the second hole.
Another object of the present invention is to provide a process cartridge and electrophotographic image forming apparatus comprising:
an electrophotographic photosensitive drum;
a developing member for developing an electrostatic latent image formed on the electrophotographic photosensitive drum, with toner;
a first frame for supporting the electrophotographic photosensitive drum;
a second frame for supporting the developing member;
an outside plate provided in the first frame and at an end thereof in an axial direction of the electrophotographic photosensitive drum;
an inside plate provided in the first frame and with a predetermined clearance to an inside surface of the outside plate;
an arm portion projecting from the second frame and interposed between the outside plate and the inside plate;
a coupling pin for coupling the first frame to the second frame to be rotatable relative to each other;
a first hole into which the coupling pin is press-fitted and which is provided in the outside plate;
a second hole of cylindrical shape into which the coupling pin is press-fitted and which is provided in the inside plate;
wherein an inside diameter of the first hole is greater than an inside diameter of the second hole;
a third hole, through which the coupling pin penetrates, for coupling the first frame to the second frame to be rotatable relative to each other, the third hole being provided in the arm portion;
a closed portion provided at a leading end of the coupling pin in a press fit direction in order to close the second hole; and
an air hole provided in the closed portion, for discharging air inside the second hole when the coupling pin is press-fitted into the second hole.